Already in the state of the art, an energy conversion device is known, intended to equip an electric driving system for such an underwater compression and pumping station. Such an energy conversion device includes at least one power module intended to ensure the energy conversion function, in a way known per se.
The energy conversion device also includes means for cooling the power module, and a sealed enclosure for housing the power module and the cooling means.
Generally, the cooling means comprise a cooling circuit in which a heat transfer fluid circulates, passing through a heat exchanger with the power module. The cooling means also comprise at least one pump for driving the heat transfer fluid circulating in the circuit.
When the energy conversion device is installed in deep waters, it is difficult or even impossible to access it in order to conduct maintenance operations therein. Thus, this energy conversion device should be able to operate without requiring maintenance for a long period, generally for at least five years.
However, the pressure difference between the heat transfer fluid circulating in the cooling circuit and the inside of the enclosure, which may for example reach 10 bars, promotes the occurrence of leaks of the heat transfer fluid from the cooling circuit towards the inside of the enclosure, notably at the static and dynamic gaskets and at fittings used for the circuit. Such leaks may also occur as a result of degradations of the cooling circuit, for example, due to ageing.
Such leaks of the heat transfer fluid reduce the lifetime of the energy conversion device, such that it may be difficult to ensure a lifetime of at least five years for this energy conversion device.